Discuss pollen and how it relates to allergies. Show some photomicrographs of pollen that illustrate the "prickly" appearance of certain types.
Some people have inherited the tendency to overproduce a certain type of antibody (IgE), which causes them to have allergic reactions to substances that do not trigger reactions in most people. Pollen from ragweed and other plants often has the tendency to trigger allergic responses because it is so abundant (ragweed relies on wind pollination). A weak antigen in most people, pollen triggers itchy eyes, runny noses, and congestion in those who are allergic to it.
Anyone can imagine the economic importance of cereal or grain crops or planted forests. But what about the economic importance of plants for medicinal purposes? For clothing or writing papers? For housing or rubber tires? Introduce to your students a number of the following examples of economically important plants.
Wheat, corn, and rice provide the bulk of the world's food staples. Other plants contribute significantly to our enjoyment of these basic foods. For example, most spices are derived from plant parts. Pepper is the ground fruit (peppers) of a variety of pepper plants. Cinnamon, oregano, cilantro, basil, lemon grass, and many other spices are all derived from plants. Coffee, tea, and colas are beverages that use extracts of beans or leaves. Certainly to the satisfaction of many a sweet tooth, sugarcane and sugar beets produce table sugar. Cotton is used for clothing and many textiles. Houses around the world are often constructed of plant parts. Many medications have been derived from plant parts, and ongoing pharmaceutical research is occurring at a breakneck pace to find plant-based compounds that can cure cancer and other major human diseases. Plant derivatives are the basis for most hallucinogenic and other illegal street drugs. With the rapid destruction of the world's tropical forests, many plants will undoubtedly go extinct before their medicinal, much less ecological, values can be fully determined.